Quantum Error Correction in SYK and Bulk Emergence

TL;DR

This paper investigates the quantum error correction capabilities of the SYK model, linking error correction, operator size, and bulk emergence, and finds that SYK nearly saturates theoretical bounds with implications for holography.

Contribution

It introduces a detailed analysis of error correction in SYK, connecting it to operator size, modular flow, and bulk duality, revealing emergent algebraic structures.

Findings

SYK's error correction properties closely match theoretical bounds.

Modular flowed correlators probe quantum extremal surfaces.

Emergent Type III$_1$ von Neumann algebra in large N limit.

Abstract

We analyze the error correcting properties of the Sachdev-Ye-Kitaev model, with errors that correspond to erasures of subsets of fermions. We study the limit where the number of fermions erased is large but small compared to the total number of fermions. We compute the price of the quantum error correcting code, defined as the number of physical qubits needed to reconstruct whether a given operator has been acted upon the thermal state or not. By thinking about reconstruction via quantum teleportation, we argue for a bound that relates the price to the ordinary operator size in systems that display so-called detailed size winding of Nezami et al. (2021). We then find that in SYK the price roughly saturates this bound. Computing the price requires computing modular flowed correlators with respect to the density matrix associated to a subset of fermions. We offer an interpretation of these correlators as probing a quantum extremal surface in the AdS dual of SYK. In the large $N$ limit, the operator algebras associated to subsets of fermions in SYK satisfy half-sided modular inclusion, which is indicative of an emergent Type III$_1$ von Neumann algebra. We discuss the relationship between the emergent algebra of half-sided modular inclusions and bulk symmetry generators.